Door control system and release mechanism

ABSTRACT

Fire control systems and release mechanisms. The release mechanisms of the present invention comprise a digital logic circuit for processing signals which are indicative of a condition in an outside environment, and for providing a trigger that will actuate the mechanical release mechanism in response to the condition, a power circuit for providing regulated power to the electronic circuit in response to the input power, the regulated power being used to operate the digital logic circuit, and a power backup circuit interfaced to the power circuit for providing the regulated power for a predetermined time in the event of an input power failure so that the digital logic circuit can be operated for the predetermined time during the input power failure.

This is a division of application Ser. No. 08/153,590, filed Nov. 17,1993, now U.S. Pat. No. 5,576,581.

FIELD OF THE INVENTION

This invention relates generally to door control safety systems, andmore particularly, to release mechanisms used in conjunction withrolling doors to ensure a safe environment in the event of acatastrophe.

BACKGROUND OF THE INVENTION

Fire doors have long been used for providing safety mechanisms toprotect an environment were an event such as the actuation of a firealarm or smoke detector occurs. Systems which utilize fire doorsgenerally receive their operating power from the electrical system of abuilding. When an alarm event occurs or the operating power is lost, arelease mechanism interfaced to the fire door causes the fire door toclose, thereby protecting the environment from the fire condition andsmoke.

A fire door system usually comprises a rolling fire door assembly thatincludes a rolling fire door mounted on a horizontally extending axlefor movement of the door between the raised (and lowered) positions.See, for example, U.S. Pat. No. 5,082,316, Wardlaw, at column 2, lines17-28, the teachings of which are specifically incorporated herein byreference.

In these systems, the fire door is maintained in the raised position bya release mechanism which is mounted on the wall above the door. Releasemechanisms are connected to release levers through a chain so that therelease lever is held in locking engagement when the chain is intension. The chain normally comprises a fusible link which is adapted tomelt and thereby release the door in response to the heat produced by afire.

There are many types of release mechanisms known in the art, examples ofwhich are disclosed in the Wardlaw patent referenced above. Generally, arelease mechanism and its associated detection system may be adjusted tocompensate for more or less severe ambient temperature changes bydifferent settings of the release mechanism, or by varying the size ofcompensating vents in the system to increase or decrease the rate ofpressure buildup caused by a sudden temperature rise. Such releasemechanisms may also be "time-delay release devices" in that they onlyrelease the fire door to close during emergency conditions after apredetermined time delay which is initiated after receiving data aboutan emergency condition, or after losing operating power.

Prior release devices have also generally used solenoids to interfacewith the temperature fuse link system and chain which drives the rollingfire door. The solenoids actuate the chain during the alarm or powerloss condition. The release devices are termed "fail safe" when thesolenoid operates or when the operating power to the system is lost.

However, the prior release mechanisms known in the art have notpossessed the ability to operate for a period of time to sense an alarmcondition when operating power is lost. This has resulted in fire doorsbeing closed only on the condition when operating power is lost but whenno fire or other emergency event is detected. Thus when power isinterrupted to the release device in response to some non-catastrophicor non-fire condition, it is generally not necessary for the rollingdoor to close. The prior rolling doors and release mechanisms haveautomatically closed in this situation, thereby presenting potentialdangers to individuals who might be trapped in-a building without power,and further requiring resetting of the fire control system. The rollingfire door art has not heretofore devised a solution to these problems.

SUMMARY OF THE INVENTION

The aforementioned problems are overcome by electronic circuits forcontrolling mechanical release mechanisms provided in accordance withthe present invention. In a preferred embodiment, electronic circuitsprovide digital logic means for processing signals which are indicativeof a condition in an outside environment and providing a trigger thatwill actuate the mechanical release mechanism in response to thecondition. The circuits further comprise power means for providingregulated power to the electronic circuit in response to input power,the regulated power being used to operate the digital logic means. Morepreferably, the circuits comprise power backup means interfaced to thepower means for providing the regulated power for a predetermined timein the event of an input power failure so that the digital logic meanscan be operated for a predetermined time during the input power failure.

It is further preferred that the electronic circuits comprise relaymeans interfaced with the digital logic means for receiving the triggerfrom the digital logic means to actuate the mechanical release mechanismin response to the condition, and more preferably, comprise poweractuation means interfaced to the relay means for providing power to therelay means to actuate the mechanical release mechanism. In yet afurther preferred embodiment, the power backup means is a capacitorhaving a capacitance value of about 22,000 microfarads. More preferably,the predetermined time that the power backup means provides regulatedpower is about 30 seconds.

In other aspects of the invention, a latch for a movable fire stop of arelease mechanism in a fire control system is provided. The latchpreferably comprises a metallic casing having geometrically regularproportions and an inside wall, a first opening adjacent the inside wallof the casing forming with the wall an open area in the form of a slothaving dimensions adapted to receive a latch plate having dimensionssuch that its width is greater than its thickness, and its length isgreater than its width.

More preferably, the latch comprises a second opening in the casingwhich intersects with a third opening in the form of a bore, one end ofwhich bore terminates in one side of the first opening and outer end ofwhich terminates below the intersection of the second opening with thethird opening and adapted to contain a resilient member. In a preferredembodiment, the latch also comprises a latch pin mounted in the thirdopening at the end opposite the accommodation of the latch pin and belowthe intersection of the second opening with the third opening, the latchpin having a detent opening in one side. In an even further preferredembodiment, the latch comprises a body of resinous material adapted tobe secured in the casing and having openings substantially conforming tothe openings in the casings for securing the latch pin and resilientmember in the casing.

The electronic circuits, latches, and fire control systems provided inaccordance with the present invention are economical to produce and arehighly reliable. Since these release mechanisms function for apredetermined time after power loss to the system, the use of releasemechanisms provided in accordance with the present invention are saferthan prior release mechanisms, since they do not cause the rolling doorto close merely on the loss of power to the system. Furthermore, withthe use of digital logic circuitry, the release mechanisms are highlyreliable, do not utilize undue amounts of power for operation, andprovide fail safe operation under all circumstances. Such results havenot heretofore been achieved in the art.

The invention will be better understood by those with skill in the artby reading the following detailed description of preferred embodimentsin conjunction with the drawings which are first described brieflybelow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are schematic representations of a fire control systemhaving a fusible link-chain subsystem interfaced with a releasemechanism provided in accordance with the present invention.

FIG. 2A shows a release mechanism of the present invention having an endlink interfaced therewith.

FIG. 2B shows the release mechanism of FIG. 2A wherein the housing ofthe release mechanism is open to expose the latch device and digitallogic circuit which comprise the release mechanism.

FIG. 3A is an isometric view of a latch device used with the releasemechanism wherein the latch device has a lever arm and an end link.

FIG. 3B is an exploded, isometric view of the latch device of FIG. 3A.

FIGS. 4A and 4B are respectively a plan and cross-sectional elevationalview of a latch device used in the release mechanism of the presentinvention.

FIGS. 5A through 5D are cross-sectional views of an ultra high molecularweight resinous body used in the latch device for holding the componentsof the latch device together.

FIG. 6 is a functional block diagram of the digital logic board whichcomprises the release mechanism provided in accordance with the presentinvention.

FIGS. 7A and 7B are a schematic of a preferred embodiment of the digitallogic board provided in accordance with the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now to the drawings wherein like reference numerals refer tolike elements, FIG. 1A shows a fire door control system 10 having arolling fire door 20 with a fusible link-chain system 30 and a releasemechanism 40. The fusible link-chain system 30 preferably comprises aseries of fusible links 50 and a standard link-chain 60 which when undertension holds the door in the open position. A housing 70 contains themechanical devices such as a detent wheel and axle, on which chain 60 isdriven to operate the rolling door 20.

In operation of the system of FIG. 1A, when a fire or other catastrophicevent occurs, the fusible links 50 melt thereby closing a circuitinterfaced to release mechanism 40 which then causes the releasemechanism 40 to be actuated and to release an end link 80. By releasingend link 80 the chain 60 is actuated by mechanical devices in housing 70which causes the rolling fire door 20 to lower in response to the fireor other catastrophic condition. The fusible links 50 can be released bya signal being received from a smoke detector detecting a smokecondition, or by other conditions caused by catastrophic events whichare sufficient to actuate the release mechanism 40.

Referring to FIG. 1B, after the catastrophic condition has occurred andthe fusible links have been activated such that the end link 80 has beenreleased from the release mechanism 40, the rolling door 20 is driven tothe closed position, thereby protecting the environment from the fire,smoke, or other condition which caused the release mechanism 40 toactuate. In this fashion, the release mechanism 40 ensures that therolling door 20 will actuate at the proper time when a safety or alarmcondition is sensed.

The release mechanism 40 is conventionally powered by "house" power inthe facility in which the control system 10 is found. Thus, releasemechanism 40 is usually wired to the 120 volt AC power line of thefacility. However, it will be recognized by those with skill in the artthat release mechanism 40 could be powered internally by a battery orother power energizing system contained within release mechanism 40.

Referring to FIGS. 2A and 2B, the release mechanism 40 comprises ahousing 90 which houses the electronics and other devices which causethe end link 80 to be released upon sensing of the fire or other alarmcondition. Optionally, housing 80 can comprise a hinged door 100 whichprotects the internal structure of release mechanism 40 and a resetbutton 110. In a preferred embodiment, the release mechanism 40 furthercomprises a transformer 120 interfaced to the 120 volt AC power supplyfound in the facility. A set of power lugs 130 allows power to bedistributed throughout the release mechanism 40 to other devices in therelease mechanism, or to the outside environment as needed.

An electronic circuit, shown generally at 140, comprises a printedcircuit board or printed wiring board and along with electroniccomponents that electronically control the operation of the releasemechanism. Preferably, a solenoid 150 is electrically interfaced to thecircuit board 140 for accepting an electrical trigger from the circuitboard 140 that will actuate the release mechanism in response to thecondition in the outside environment. Preferably, solenoid 150 isnormally de-energized; that is, it is not under power before beingactuated by the trigger event from the electronic circuit board 140.

Solenoid 150 is interfaced to a latch device, shown generally at 160,which is attached to the end link 80. The latch device comprises a leverarm 170 having two ends. Solenoid 150 is attached on a first end of thelever arm 170, and at the other end the lever arm is interfaced with theinner mechanisms of the latch. Upon receiving the trigger the solenoidis energized, thereby actuating the lever arm 170 which causes the latch160 to release end link 80, to cause the rolling door 20 to traverse tothe closed position.

Referring to FIGS. 3A and 3B, the latch comprises an outer casing 180having substantially, geometrically regular proportions and an insidewall 190. A first opening, shown generally at 200, adjacent the insidewall 190 forms an open area in the form of a slot which has dimensionsthat are adapted to receive the end link 80 which is sometimes called a"latch plate". Preferably, the latch plate 80 has dimensions such thatthe width of the latch plate is greater than the thickness, and thelength of the latch plate is greater than the width.

Referring to FIGS. 4A and 4B, a second opening 210 in casing 180intersects with a third opening 220 which forms a bore through the latch160. One end of bore 220 terminates in one side of the first opening 200and the other end of bore 220 terminates below the intersection of thesecond opening 210 with the bore 220.

In a preferred embodiment, a latch pin 230 is mounted in the bore 220 atthe end intersecting with the first opening 200. Even more preferably, aresilient member 240 is mounted in the bore 220 at the end opposite theaccommodation of latch pin 230 below the intersection of the secondopening 210 with the bore 220. More preferably, the resilient member 240is a spring. In still a further preferred embodiment, the latch pin 230comprises a detent opening in one side of the latch pin for interfacingwith the lever arm 170.

In operation of the latch 160, the lever 170 accommodated in the secondopening 210 releases end link 80 by pivoting on a pivot pin showngenerally at 250. Yet more preferably, the lever 170 further comprisesbiasing means 260 at the end of the lever 170 for moving the end of thelever and by biasing the latch pin 230 against the resilient spring 240.The latch pin 230 is biased by the resilient spring 240 to extend fromthe bore 220 into the first opening 200 at the location at which thelatch pin 230 is received in an opening in the latch plate 80 when thelatch plate is accommodated in the first opening 200.

The latch 160 further comprises an adjustable stop 270 extending fromthe casing 180 into the first opening 200 to limit the passage of thelatch pin 230 toward the casing 180. Preferably, the adjustable stopcomprises a threaded member which is threaded through the casing 180.

In yet a further preferred aspect of the invention, the latch 160comprises a body of resinous material, shown generally at 280, which isadapted to be secured in casing 180. The resinous body 280 has openingswhich substantially conform to the first, second and third openings inthe casing for securing the latch pin and resilient member in the casingand also for accommodating the lever 170. In a preferred embodiment, theresinous material is a plastic material having a sufficiently highcoefficient of friction to allow the moving parts of latch 160 tosmoothly and easily operate. The purpose of the resinous material 280 isto hold the mechanical components of latch 160 within the casing and toallow the moving parts in the casing to traverse therein with ease andefficiency. The resinous material is preferably a high density polymermaterial having an ultra high molecular weight ("UHMW") which can bemachined to form the various openings required therein and which can beconformed to the shape of the casing 180 comprising the latch 160.

Referring to FIGS. 5A through 5D, alternative embodiments for securingthe block of resinous material 280 within housing 180 are illustrated.The casing 180 shown in FIG. 5A is preferably made of aluminum. In apreferred embodiment, a 1/8 inch dowel 290 anchors the resinous material280 to the casing. The UHMW polymer block 280 can be drilled so thatdowel 290 can be passed therethrough to anchor the UHMW block 280 tohousing 180. Alternatively shown in FIG. 5C, anchoring slots 300 can bemachined from UHMW block 280 such that a ball or knob pin, showngenerally at 310, can be anchored within the openings 300. The head 320of knob pin 310 is adapted to be anchored in the UHMW block 280, whilethe shaft 330 secures UHMW block 280 to housing 180.

In yet a further preferred embodiment shown in FIG. 5D, a series of highdensity polystyrene foam shims 340 can be placed between UHMW block 280and housing 180 to frictionally hold UHMW block 280 within housing 180.

The electronic control circuitry of the present invention providesefficient means whereby fire protection can be realized using grills,counter shutters, sectional doors, counter doors, and rolling andswinging fire doors beyond that afforded by simple temperature fuselinks, or passive multiple component electromagnetic devices found inprior systems. The electronic circuitry of the present invention alsoprovides fail safe release device action according to currentUnderwriter Laboratory standards and provides releasing action asdictated by appropriate automatic or manually activated fire systemsignalling equipment.

Referring to FIG. 6, in accordance with the invention the electroniccircuit 140 comprises a digital control logic block 350 which preferablyutilizes discrete CMOS circuit elements for forming the various logicfunctions required to operate the release mechanism. More preferably,input power is received from the AC line or battery through atransient/overvoltage protection circuit 355. The voltage which isoutput from transient/overvoltage protection circuit 355 is input to apower regulation, conditioning and distribution network 360 whichconditions the voltage so that the digital control logic block 350 canbe run with reliability and accuracy.

In accordance with the present invention, power backup circuit 370 isinterfaced with the power regulation, conditioning and distributioncircuit 360 to provide the regulated voltage to digital control logicblock 350 in the event that the input power is lost.

A solenoid trigger power actuation circuit 380 is interfaced to digitalcontrol logic block 350 which will trigger the solenoid 150 when thedigital control logic block 350 senses an alarm condition due to a fireor other catastrophic emergency. Digital control logic 350 preferablycomprises fused diode gated and protected inputs which are interfaced toForm A and Form B initiating devices shown generally at 390 and 400respectively, as well as a Form C initiating device 410.

The Form A, Form B and Form C initiating devices are triggered throughinitiation logic 420 which is directly interfaced to the digital logicblock 350. Additionally, a proximity/lower door closure unit 430provides limit sensing contacts for door 20 and provides feedback to thedigital control logic block 350 so that the status of the position ofthe door before, during and after the emergency condition can be sensedby digital control logic block 350. The Form A, Form B, and Form Cinitiating devices along with the proximity/lower unit protection block430 perform status processing functions for the electronic circuit ofthe present invention to control operation of the fire protectionsystem.

More preferably, digital logic block 350 is interfaced to a powersensing circuit 440 which senses whether power is present through thetransient/overprotection block 355. If the power is not present, thedigital control logic block 350 will output an alarm signal which can bedetected by personnel in the outside environment of the fire controlsystem. Additionally, motor sense circuity 450 is interfaced withdigital control logic block 350 to determine whether a motor whichdrives the door 20 is properly functioning.

The motor sense circuitry is further preferably interfaced with a24-volt AC motor control voltage block 460 through which the motorcontrol voltage is input. In still a further preferred embodiment, thefire control system comprises a Form C output block 470 which caninterface with a Form C output device and a 12-volt DC auxiliary outputblock 480 that provides 12 volts auxiliary voltage for use off-board.Additionally, a test button 490 is interfaced with the digital controllogic block 350 to provide manual testing of the Form A, Form B, or FormC initiating devices.

The electronic circuit 140 which controls the mechanical releasemechanism of the present invention is shown schematically in FIGS. 7Aand 7B. In a preferred embodiment, digital block 350 contains digitalcircuit elements that process signals which are indicative of acondition, such as a fire, in an outside environment. The digitalcircuitry of block 350 thereby provides triggering signals that willactuate the mechanical release mechanism of the present invention inresponse to an alarm event induced by an alarm condition.

It is desired to provide regulated power to the electronic circuit sothat the digital circuitry of block 350 can be run with reliability andaccuracy. To accomplish this goal, input power is provided to theregulated power block 360 which outputs regulated power to the digitalcircuit block 350. The regulated power is shown on the circuit diagramof FIGS. 7A and 7B as V_(cc1) which is preferably a regulated DC voltagelevel of about 15 volts DC.

In accordance with the present invention, the electronic circuit ofFIGS. 7A and 7B is fail-safe and can operate in the event of powerfailure to the system. To accomplish this result, power backup circuit370 is provided to the electronic circuit. The power backup circuit 370is interfaced to the regulated voltage supply 360 and will provideregulated power for a predetermined time in the event of an input powerfailure. By assuring that the regulated power is present for apredetermined time in the event of input power failure, the digitalblock 350 will continue to operate for the predetermined time during theinput power failure so that the mechanical release mechanism willperform the job of releasing the fire door during a fire emergency.

In a further preferred embodiment, the circuit of FIGS. 7A and 7B isinterfaced with solenoid 150 that releases an end latch of themechanical release mechanism when a signal is received from the circuit.To further ensure that the device of the present invention is fail-safe,power actuation circuit 380 is provided to actuate the solenoid when atriggering signal is received from the digital block 350. The poweractuation circuit 380 comprises a relay, shown as K1, which is in the"normally open" position during circuit operation.

In the event of an alarm condition, relay K2 of digital block 350 whichis "normally closed" interfaces a signal to relay K1 to throw thenormally open switch to the normally closed position, thereby providinga ground path between the power capacitor 500 in the power actuationblock 380 through the relay K1. Discharge of the power capacitor 500through relay K1 causes the solenoid to release the end link 80 in therelease mechanism so that the fire door can be closed by appropriatemechanical apparatus in the system. The power capacitor 500 ispreferably a 22,000 microfarad capacitor which is continuously chargedthrough V_(cc1) during circuit operation.

In yet a further preferred embodiment, the power backup block 370comprises a similar 22,000 microfarad power backup capacitor 510 whichis continuously charged by regulated power supply 360. In the event ofpower failure, the power backup capacitor provides power to the digitallogic block 350 for about 30 seconds so that power is available to thelogic circuitry for operation during power failure. This allows thepower actuation capacitor to discharge through relay K1 when relay K2receives an alarm from the powered digital logic block 350.

More preferably, power is supplied to the power regulation conditioningand distribution network 360 directly through lugs 1 and 2. If 24-voltAC or 24-volt DC power is applied, the power can be applied directly tothe network. However, if 120-volt power is applied, it is firstconditioned through the transformer 120 which is preferably a 6-1stepdown transformer. Diode bridge 520 provides full wave rectificationfor AC input power. For DC input voltage, three of the four diodes areremoved, and one of the diodes is installed as a diode switch with a busshort to provide circuit ground.

Input protection is provided by a 3/4 amp fast blow fuse 530 incombination with resistor R29, zener diode 540 and the 470 microfarad,50-volt capacitor shown at 550. A surge limiting resistor, R29, reduceselectrical stress on the diode bridge 520 and capacitor 540 anddecreases the effects of line and lead inductance, thereby optimizingthe response of the transient voltage suppression diode 540. Capacitor550 functions primarily to filter rectified voltage provided by he diodebridge 520. Integrated circuit 560 is preferably a 7820 timer andprovides a regulated 20 volts DC to the second integrated circuit 570,preferably a 7815 timer. Integrated circuit 570 provides a regulated15-volt system voltage, V_(cc1).

Diode D8 is a switch which prevents the power backup capacitor 510 fromdischarging through its normal charge path. This accounts for theability of the circuit of FIGS. 7A and 7B to monitor and process alarmsignals during short periods of acute power loss and brown-outconditions. Backup capacitor 510 provides a capacitive type of powersupport to the CMOS logic devices and ultrasensitive relays which areutilized in the circuit. Diode D25 provides protection against positivegoing transients and further provides an auxiliary supply output ofapproximately 4.4 volts DC for use with equipment such as closeproximity smoke detectors and dedicated release devices.

Diode D16, found in the solenoid trigger circuit 380 in a preferredembodiment provides a voltage source for the normally closed Form Balarm processing loop. Also in the solenoid trigger circuit 380, diodesD24, D15 and resistor R21 charge power capacitor 500 through relay K1 sothat power can be sourced through the chassis-mounted solenoid 150(shown off-board in the circuit diagram of FIGS. 7A and 7B) under analarm condition. In accordance with the present invention, an "alarm" isdefined as about a 1 to 10 second time period after an alarm-out loopinterruption is sensed, or a loss of input power from about a 1 to 30second time period. These two delay periods are verification delays, andcan be adjusted in the circuit by variable resistors VR1 and VR2 inaccordance with the invention.

Resistors R1 and R2 comprise a voltage-dividing network that providesinput power to the digital control logic block 350. The power isprovided to AND gate 580 at pin 6. Preferably, pin 5 of AND gate 580 isthe input for a fire alarm status through pin 11 of second AND gate 590.The output, pin 4, of AND gate 580 drives the base of transistor Q5which switches the trouble detection relay K2. In this fashion, lugsTB1-8, TB1-9, and TB1-10 provide the Form C contacts out for theauxiliary trouble/alarm switching signals received from relay K2.

In a more preferred embodiment, diode D9 in combination with resistorsR3 and R4, capacitor C6 and VR1 provide an input to integrated circuit600 which in a further preferred embodiment is a Schmitt trigger NANDgate. This combination provides a power loss processing loop for thedigital control logic block 350. Schmitt trigger 600 provides a reliablelogic transition in response to a slow change in the power loss timinginput. Similarly, diode D8 in combination with resistors R6, R7,capacitor C7 and VR2 provide input to Schmitt trigger 600 at pin 2 tocontrol process alarm loop signals in a reliable fashion.

The combination of diodes D21, D12, D24, resistors R24, R25, R22,transistor Q4 and integrated circuit 610 (also a 4081B AND gate)comprise the proximity/lower unit detection block 430 of circuit 140.This combination provide a status processing function of external lowerlimit door contacts at a normally open or normally closed set ofswitches. When the door 20 is in a closed position and the appropriateinputs are connected to the lower limit detection unit 430, AND gate 610drives pin 3 of NAND gate 620 low which thereby inhibits the releasemechanism. This prevents the releasing mechanism from attempting tolower a previously closed door and eliminates the concern of damagingthe door and motor controls.

When the door 20 is an automated motorized door, gate 620, integratedcircuit 625, resistors R16 and R15, capacitors C8 and C9, and diodesD10, D11, and D12, along with fuse 630, form the 24-volt AC motorcontrol circuit 460 which prevents closure of the door by the releasemechanism if the motor control secondary winding voltage is present. Thesample voltage from the motor control circuitry 460 is introduced to themotor sense processing logic via the two lugs TB2-1 and TB2-2. When thisvoltage is present, the release mechanism of the present invention willallow the automated door 20 to close by motorized means. In the absenceof the secondary voltage, closure will be initiated by the releasedevice exclusively.

In a further preferred aspect of the invention, AND gate 640 resistorsR26, R27, and R28, transistor Q3, and light emitting diode 650, comprisethe motor sense circuit 450 which provides an enable or disableindicator for both the motor sense circuit 450 and door edge/lower limitprotection unit 430. If either circuit 430 or circuit 450 is active, LED650 will be illuminated.

Finally, the Schmitt trigger NAND gate 620, resistors R17, R18,capacitors C10 and the actuation capacitor 500 trigger the solenoidthrough relay K1 in the event of an alarm, power loss, or othercatastrophic failure of the control logic circuitry. This provides afail safe mode for the release device in full compliance with allregulatory requirements and standards.

Thus, the fire control systems, release mechanisms, and electroniccircuitry provided in accordance with the present invention incorporatestate-of-the-art electronic control, and provide maximum fire protectionunder all circumstances. Circuits described herein can be used alone orin conjunction with integrated, fused link systems and provide powerloss backup and supervisory support to a release device in a firecontrol system. Furthermore, the special diagnostic capabilitiesprovided by circuits claimed and described herein, such as door edgesensing and motor control monitoring, ensure that fire control systemswill function in the event of any catastrophic event which provides analarm to the system. Such results have not heretofore been achieved inthe fire control art.

There have thus been described certain preferred embodiments ofelectronic control systems provided in accordance with the presentinvention. While preferred embodiments have been described anddisclosed, it will be recognized by those with skill in the art thatmodifications are within the true spirit and scope of the invention. Theappended claims are intended to cover all such modifications.

What is claimed is:
 1. A latch for a movable fire stop of a releasemechanism in a fire control system comprising;a metallic casing havingan inside wall; a first opening adjacent the inside wall of the casingforming with the wall an open area in the form of a slot havingdimensions adapted to receive a latch plate having dimensions such thatits width is greater than its thickness and its length is greater thanits width; a second opening in the casing which intersects with a thirdopening in the form of a bore, one end of which bore terminates in oneside of the first opening and the other end of which terminates belowthe intersection of the second opening with the third opening andadapted to contain a resilient member; a latch pin mounted in the thirdopening at the end intersecting with the first opening for engaging thelatch plate, a resilient member mounted in the third opening at the endopposite the latch pin and below the intersection of the second openingwith the third opening, the latch pin having a detent opening in oneside; a lever means accommodated in the second opening for biasing thelatch pin and releasing an end link of the latch plate, the lever meansbeing adapted to pivot on a pivot pin; and a lever biasing meansconnected with an end of the lever means for moving the end of the levermeans to bias the latch pin against the resilient member.
 2. The latchrecited in claim 1 wherein the latch pin is biased by the resilientmember to extend from the third opening into the first opening wherelatch pin receiving opening in the latch plate will be positioned whenthe latch plate is accommodated in the first opening.
 3. The latch inclaim 2 further comprising electrical circuit means for detectingenvironmentally detrimental conditions and activating the lever biasingmeans to move the latch pin from within the latch pin receiving openingin the latch plate.
 4. The latch recited in claim 3 wherein the casingis formed from a segmented aluminum structural section.